The present invention relates to a holding arrangement for a planar workpiece with an at least partially encircling band-like edge face, a carrier arrangement with at least one such holding arrangement as well as uses for the holding arrangement and stated carrier.
The starting point of the present invention is the problem of holding thin, disk-shaped workpieces such as, in particular, disks for the fabrication of storage disks, be they CDs, hard disks or magneto-optical storage disks or semiconductor wafer disks. The considered holding device is intended for use during surface treatment processes on workpieces such as during PVD or CVD coating processes of all known variants as well as their mixed forms such as PECVD (plasma enhanced CVD), further for etching processes and thermal processes, wherein most of these processes are vacuum processes, CVD or thermal processes, but not necessarily.
In most of the Just outlined technical fields the problem of holding resides in that thin disks, down to thickness dimensions of 0.5 mm with diameters of .gtoreq.2 cm up to 10 and more cm, must be held, and the following conditions must be optimally fulfilled:
a) The smallest possible areas of the workpiece surfaces should be covered or shadowed with respect to the intended treatment process. PA1 b) It should be possible to absorb dimensional changes, brought about thermally, of the workpieces if possible free of tension, in order to prevent warping of the workpieces or even fractures. PA1 c) When placing and removing the workpieces from the holding device the danger of scratches should be minimal as well as also the friction taking place, with which concomitantly, friction particle contamination for the surface treatment is to be minimized. PA1 d) The stated workpieces are to be subjected to defined holding forces by the holding device. PA1 e) The holding device is to be suitable to be loaded or unloaded by automatic handling robots. PA1 f) The holding device should make possible the optimally dense workpiece holding on a carrier for several workpieces. PA1 g) Loading and unloading the holding device should be simple, should require low force and time expenditures for the purpose of economical operation in production. PA1 a) Since the spring bars engage the planar workpieces at their edge and at locations distributed around their edge, all undesired covering of the workpiece surface which conventionally is to be primarily uniformly surface-treated, is avoided. PA1 b) Since the spring bars are mounted in receptacles and can bend out resiliently, suitable dimensioning of the spring bars and the receptacles will result in the least possible load on the workpiece even under thermal expansion and/or an even distribution of tension around the workpiece periphery. PA1 c) Because, during loading or unloading of the workpieces, a relative motion between the workpiece surface and the holding arrangement according to the invention does not need to take place, but rather the workpiece can be inserted only straight along its band-like encircling edge face into the holding arrangement--between the spring bars--which are extremely thin, an extremely low danger of damage to the planar workpiece surface results and due to the very short frictional action paths, extremely low frictional stress and consequently an optimally low danger of contamination of the treatment process through friction particles, occurs. PA1 d) Since the total spring characteristic of the holding arrangement according to the invention is defined by the characteristics of the essentially linear spring bars, and their support in the receptacles in the frame, the forces which act radially inwardly upon the planar workpiece on its band-like circulating edge face, are defined. PA1 e) Due to the extremely simple insertion and withdrawal motion by which a planar workpiece can be inserted between the spring bars or removed therefrom, and a handling lift which for this purpose is small, the arrangement according to the invention is extremely well suited for automatic handling. PA1 f) Due to the fact that the holding arrangement according to the invention, viewed from a workpiece radially outwardly, requires only just the space for the spring bars and the provided receptacles on the frame, on a carrier for several holding arrangements for several workpieces the latter can be packed extremely tightly together and consequently the carrier surface can be utilized optimally. PA1 Different spring bar polygons can be flexibly disposed on the same frame. PA1 Polygons which have an extraordinary large number of corners can be used. In that case preferably the spring bars between the corner portions are bent radially inwardly in order to form engagement portions on the workpiece edge which are offset from the groove radially inwardly. PA1 The spring bars or the spring bar polygon are guided or supported precisely.